SHORT COMMUNICATION: Mineral assessment of rangeland-managed beef cows in the high desert region of Oregon

Objective: Our objective was to assess the mineral status of rangeland-managed beef cows and available forages in the Oregon high desert, which is currently unknown. Materials and Methods: Mineral concentrations were measured at the end of the annual grazing season from common range forage plants and 30 randomly selected beef cows on communal range (10 cows per group): unsupplemented Angus (UA), unsupplemented Longhorn (UL), and Angus cows supplemented before the grazing season with minerals and true protein ( SA). CONTRAST statements in PROC GLM were used to determine the effect of breed (UL vs. UA) and winter mineral and protein supplementation (SA vs. UA). Results and Discussion: Imbalanced mineral concentrations (minerals above and below respective minimum requirements) were observed in common range forage plants and beef cattle; most beef cows were deficient for copper, sodium, selenium, and zinc. Specifically, serum selenium concentrations of unsupplemented cows were in the clinical deficiency range (2-21 ng of Se/mL). Whereas breed did not alter serum mineral concentrations, mineral and protein supplementation during winter improved serum concentrations of selenium at the end of the fall season to marginally deficient concentrations between 53 and 90 ng/mL. Implications and Applications: Imbalanced mineral concentrations are prevalent in beef cows after grazing the Oregon high desert range, which can be in part improved through mineral and protein supplementation over winter. Blood analysis from a subset of animals on return to the winter feeding grounds would help to formulate a mineral supplement that addresses specific cow requirements during the winter feeding period.